1. Field of the Invention
Methods and apparatuses consistent with the present invention relate to a relay system. More particularly, the present invention relates to a method and apparatus for controlling power in a decode-and-forward (DF) relay system.
2. Description of Related Art
A relay system may acquire a diversity gain through a cooperation between network nodes by using a relay scheme. The relay scheme includes an amplify-and-forward (AF) protocol and a decode-and-forward (DF) protocol. In the AF protocol, a relay amplifies a received signal to retransmit the received signal. Conversely, in the DF protocol, the relay completely decodes the received signal and then re-encodes the decoded received signal and thereby transmits the encoded received signal.
Accordingly, in the case of an AF relay scheme, since a relay retransmits a received signal without decoding the received signal, noised contained in the received signal is also amplified during a retransmission process. Also, in the case of a DF relay scheme, when an error occurs during a decoding process, an error propagation occurs even in a signal to be encoded and then transmitted. A cooperative diversity technology utilizes the AF relay scheme, the DF relay scheme, and the like. Also, the cooperative diversity technology can provide a high data transmission rate, an improved service quality, and an excellent network capacity in various wireless networks, such as a limited frequency spectrum, complex space-time, and the like, and thus the cooperative diversity technology is gaining popularity.
In this instance, specific research related to a relay system using the cooperative diversity technology is being currently performed. Particularly, technologies and experimental data are insufficient in association with communications of the relay system using the DF relay scheme.
In a conventional method and apparatus for controlling power in a DF relay system, since a power of a signal at a source node or a relay node is maintained to a uniform level, link reliability and throughput may be reduced.
Also, since the power is uniformly maintained at all times, the efficiency of the power may be reduced. Particularly, in the DF relay scheme, the above-described problems become an issue.
Therefore, a method and apparatus for controlling power in a DF relay system is required.